Their friendship continued to grow playing together for England before they took on one another at Stamford Bridge on Saturday.
Rice emerged triumphant from the match, with West Ham winning 1-0, revenge for when Mount had the better of the two the previous time they had been on opposing sides.
"It was a pre-season game for the Under-23s," Rice recalled on West Ham’s official website before the match. "I remember, we lost 3-1 and he scored a 'worldy'.
"Now we’ve got the big game on the weekend in the Premier League, which is everything we’d dreamt of.
"It’s going to be absolutely massive. It’s a London derby and massive for the fans and obviously my best friend will be on the pitch, so it’s going to be really special.
"It’s going to be a weird experience, but also a really special experience and one we’re both going to be buzzing off."
Ahead of the match the pair shared their memories of growing up together, life at the Chelsea academy and Mount’s prank video of Rice on holiday that went viral.